Sahih Muslim · Hadith 5714
The Book on General Behaviour - كتاب الآداب
وحدثنا أبو كريب، حدثنا أبو معاوية، عن الأعمش، بهذا الإسناد وقال " إنما جعلت قاسما أقسم بينكم " .
This hadith has been reported on the authority of A'mash with the same chain of transmitters but there is a slight variation (of wording) that, instead of the word Bu'ithat (I have been sent), the word ju'ilat (I have been made) has been used.
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).